Synthesis of ansa-metallocene catalysts

ABSTRACT

A process of preparing in high yield ansa-metallocene complexes and rac ansa-metallocene complexes by reacting an ansa-bis-cyclopentadiene compound with a metal amide complex.

GRANT REFERENCE

The invention here set forth was partially funded by the National Science Foundation Grant #CHE90-22700 Amend 02 and the government may have certain rights in the invention.

CROSS-REFERENCE TO A RELATED APPLICATION

This application is a continuation-in-part of Jordan et al., Ser. No. 08/252,591 filed Jun. 1, 1994, now U.S. Pat. No. 5,495,035.

BACKGROUND OF THE INVENTION

This invention relates to the field, now well established, of use of ansa-metallocenes as catalysts. They are particularly useful as catalysts for the polymerization of ethylene and alpha olefins such as propylene.

Conventional heterogeneous catalysts such as Ziegler-Natta systems have a variety of active sites, only some of which are stereo-specific. Obtaining a polymer with specific properties can involve a considerable amount of trial and error in order to find the best combination of catalyst, co-catalyst and stereo-regulator. In contrast, however, the active polymerization site in a metallocene catalyst is well defined, and can be modified in a straightforward manner via modification of the cyclopentadienyl ligands, enabling the structure of the polymer to be controlled with far greater precision.

A simple metallocene catalyst for polymerizing ethylene is (C₅ H₅)₂ ZrCl₂ which consists of a zirconium atom bound to two chlorine atoms and two cyclopentadienyl rings, and which is activated by co-catalysts such as methylaluminoxane (MAO). During the 1980's, ansa or bridged metallocenes, in which the cyclopentadienyl rings are linked by a chemical bridge, were found to be particularly useful for the polymerization of olefins. In particular, ansa-metallocene complexes, when used in combination with a co-catalyst such as methylaluminoxane (MAO), polymerize propylene to highly isotactic polypropylene, highly syndiotactic polypropylene, or atactic polypropylene, depending on the structure of the ansa-metallocene used.

As is well known, isotactic polymers have each pendant group attached to the backbone in the same orientation, whereas in syndiotactic polymers, these groups alternate in their orientations and atactic polymers have a random arrangement of the groups along the backbone. Since the stereochemistry of the polymer has a great effect on its properties, it is desirable to control this feature. Chiral, C₂ -symmetric ansa-metallocenes produce isotactic polypropylene.

While the greatest area of potential use for ansa-metallocene catalysts currently is for polymerization of olefins, such as ethylene and propylene, they also have significant uses as catalysts or catalyst precursors for other reactions where stereo-selectivity is important.

The utility of ansa-metallocene complexes as catalysts for olefin polymerization and other reactions has created a high demand for a practical synthesis of ansa-metallocene compounds.

In spite of this demand, current procedures for the synthesis of Group 4 (Ti,Zr,Hf) ansa-metallocenes require the use of ansa-bis-cyclopentadienyl dianion reagents and are hampered by low yields and tedious isomer separation and purification steps. Some of these problems have been discussed in Ellis, W. W.; Hollis, T. K.; Odenkirk, W., Whelan, J.; Ostrander, R.; Rheingold, A. L.; Bosnich, B. Organometallics 1993, 12, 4391. In particular, the synthesis of chiral C₂ symmetric ansa-metallocenes typically produces mixtures of desired rac (racemic) and undesired meso isomers. A typical synthesis of an ansa-metallocene complex is shown in equation 1 below: ##STR1##

This equation is typical of the process as shown in the art. See for example Spaleck, W.; Kuber, F., Winter, A.; Rohrman, J.; Bachmann, B.; Antberg, M.; Dolle, V.; Paulus, E. F. Organometallics 1994, 13, 954. Stehling, U.; Diebold, J.; Kirsten, R.; Roll, W.; Brintzinger, H. H.; Jungling, S.; Mulhaupt, R.; Langhauser, F. Organometallics 1994, 13, 964. Halterman, R. L. Chem. Rev. 1992, 92, 965. See also, for example, U.S. Pat. No. 5,145,819, U.S. Pat. No. 5,268,495, and EPA 0-530-908-A1.

By way of further example, an important chiral Group 4 ansa-metallocene is rac-(EBI)ZrCl₂ (EBI═ethylene-1,2-bis(1-indenyl) which is currently prepared from ZrCl₄ and the dianion of the EBI ligand (Halterman, R. L. Chem. Rev. 1992, 92, 965). Brintzinger (Wild, F. R. W. P.; Wasiucionek, M.; Huttner, G., Brintzinger, H. H. J. Organomet. Chem. 1985, 288, 63) and Collins (Collins, S.; Kuntz, B. A.; Hong, Y. J. Org. Chem. 1989, 54, 4154; Collins, S.; Kuntz, B. A.; Taylor, N. J.; Ward, D. G. J. Organomet. Chem. 1988, 342, 21) used (EBI)Li₂ and reported low, variable yields (20-50%) of rac-(EBI)ZrCl₂. Buchwald employed (EBI)K₂ and obtained (EBI)ZrCl₂ in a rac/meso ratio of 2/1 in 70% yield. Grossman, R. B.; Doyle, R. A.; Buchwald, S. L. Organometallics 1991, 10, 1501. In general, current synthetic procedures produce the desired rac-ansa-metallocenes in 10%-30% yield after tedious separation and purification steps, and even then separation of the rac from the meso products is not always possible.

Lappert et al. (Chandra, G.; Lappert, M. F. J. Chem Soc. (A) 1968, 1940) reported that certain Group 4 metallocene complexes are formed by the reaction of Group 4 metal amide complexes with cyclopentadiene compounds. However, this reaction yields only mono-cyclopentadienyl products when the metal is titanium, or when the cyclopentadiene compound is indene. This was ascribed to steric hindrance which disfavors addition of the second cyclopentadienyl ligand when the metal is small (titanium) or the cyclopentadienyl ligand is bulky (indenyl). Hefner, et al., also (U.S. Pat. No. 5,194,532) discusses the preparation of (indenyl)Ti(NMe₂)₃ by reaction of indene and Ti(NMe₂)₄. Ansa-metallocene complexes are not discussed in the Lappert or Hefner references.

There is, therefore, a need for a process which would produce ansa-metallocene complexes in high yield. Additionally, there is a need for a process which would produce rac ansa-metallocenes in high yield without contamination by the meso isomer, since the rac isomer is most useful in stereoselective catalysis. The present invention has as its primary objectives the fulfillment of these needs.

It is another objective of the present invention to prepare rac ansa-metallocenes by means of a single step process, in most instances in yields of 50% or higher, without the use of ansa-bis-cyclopentadienyl dianion reagents.

SUMMARY OF THE INVENTION

The process of preparing rac ansa-metallocene complexes in high yield by reacting an ansa-bis-cyclopentadiene, indene, fluorene, or substituted derivative thereof with a metal amide complex wherein the metal is a Group 3, 4 or 5 metal, but preferably zirconium, and R and R' (eq. 2) are the same or different, preferably hydrogen or C₁ to C₂₀ hydrocarbyl radicals, and more preferably C₁ to C₄ alkyl and most preferably methyl. In some embodiments the amide complex may be replaced with a corresponding phosphide (PRR') or sulfide (SR) complex.

DETAILED DESCRIPTION OF THE INVENTION

In the present invention, ansa-metallocene complexes of general formula ##STR2## are prepared by reaction of metal amide complexes with ansa-bis-cyclopentadiene compounds as illustrated in eq. 2. ##STR3##

R and R' represent hydrogen or hydrocarbyl radicals having from 1 to 20 carbon atoms, preferably from 1 to 4 carbon atoms. R and R' may also be silyl radicals SiR₃. R and R' may be the same, different or linked.

Cp independently in each occurrence is a cyclopentadienyl, indenyl, fluorenyl or related group that can π-bond to the metal, or a hydrocarbyl, alkyl, aryl, silyl, halo, halohydrocarbyl, hydrocarbylmetalloid, or halohydrocarbylmetalloid substituted derivative thereof. Cp may contain up to 150 nonhydrogen atoms.

X may be any bridging or ansa group that is used to link the Cp groups, including, for example, silylene (--SiH₂ --) or substituted silylene, benzo (C₆ H₄) or substituted benzo, methylene (--CH₂ --) or substituted methylene, ethylene (--CH₂ CH₂ --), or substituted ethylene bridges.

M represents the metal used and is usually a Group 4 metal selected from the group consisting of titanium, zirconium and hafnium, but may also be a Group 3 (Sc,Y,La) or Group 5 (V,Nb,Ta) metal. Preferably it is a Group 4 metal, and most preferably it is zirconium.

n is a whole number and is from 3 to 5. When M is a Group 4 metal "n" is 4, when M is a Group 3 metal "n" is 3, and when M is a Group 5 metal "n" is 5.

In particular, the rac isomers of chiral C₂ -symmetric ansa-metallocenes are prepared in high yield. An example is the reaction of Zr(NMe₂)₄ with 1,2-bis(3-indenyl)ethane ((EBI)H₂), shown below (eq. 3). This reaction provides an efficient, high yield synthesis of pure rac-(EBI)Zr(NMe₂)₂, which can easily be converted to rac-(EBI)ZrCl₂ and related derivatives. ##STR4##

The process of making each starting material for this reaction is known. In particular, the synthesis of ansa-bis-cyclopentadienes such as (EBI)H₂ is described in Halterman, R. L. Chem. Rev. 1992, 92, 965, and references therein.

The metal amide complexes M(NRR')4 can be prepared by reacting the corresponding metal tetrahalide complex such as zirconium tetrachloride with an appropriate lithium amide, see D. C. Bradley and I. M. Thomas, Proc. Chem. Soc., 1959, 225; J. Chem. Soc. 1960, 3857. As earlier indicated, it is preferred that R and R' be hydrogen or C₁ to C₂₀ hydrocarbyl radicals and preferably C₁ to C₄. Methyl is the most preferred and is illustrated in eq. 3.

The reaction between the ansa-bis-cyclopentadiene and the metal amide can take place at any temperature from -80° C. to ambient, i.e., about 25° C. on up to 250° C., but is preferably within the range of 80° C. to 160° C. At 100° C. the reaction is typically complete in less than 24 hours, and perhaps as few as 3 to 5 hours.

The dimethylamine produced as a by-product in eq. 3 is gaseous. It is preferred that this not be completely swept away by gas flushing during the reaction as it is believed that it may catalyze the conversion of initially formed meso product to the desired rac product, therefore, ultimately yielding a higher ratio of rac/meso. This is believed the case because it has been observed that when the reaction flask is flushed with inert gas during the reaction, the yield of desired rac product decreases significantly.

While the use of metal amide complexes as starting materials is discussed above, if the NRR' groups are replaced with PRR' or SR groups, it is expected that equivalent results will be achieved. Likewise, amide complexes of the Group 3 metals, (Sc,Y,La) and Group 5 metals (V,Nb,Ta) may also be used, and it is expected that equivalent results will be achieved.

It is also expected that use of chiral, enantiomerically enriched metal amide complexes in equation 2 will allow the synthesis of enantiomerically enriched ansa-metallocenes.

The reaction desirably is conducted in the presence of a nonaqueous, nonalcoholic solvent that at least partially dissolves one of the reactants. Typical of such solvents are hydrocarbons such as benzene, toluene, nonane, m-xylene and hexane, simple ethers, chlorinated hydrocarbons, such as chlorobenzene, acetonitrile, tetrahydrofuran, etc.

It is believed that the metallocene amide complexes which are produced in eq. 2 may, when activated by a suitable cocatalyst, be used as catalysts in many applications. Alternatively, the metallocene amide complexes which are produced in eq. 2 may be converted to the more commonly used metallocene chloride complexes by a simple protonation reaction as described in Hughes, A. K.; Meetsma, A.; Teuben, J. H., Organometallics 1993, 12, 1936. The metallocene amide complexes which are produced in eq. 2 may also be converted to other derivatives, such as metallocene alkyl complexes.

While the above description has been provided with metal amides: M(NRR')_(n), it is possible to use other leaving groups and to even further generalize the reaction (Eq. 4). ##STR5## Here "Y" can be other leaving groups besides NRR', such as alkyl (R), alkoxy (OR), SR, PRR', F, Cl, Br, I, OC(O)R, OS(O)₂ R, with Y groups being the same or different or linked (chelating). The R and R' are as previously defined and also they may be the same or different or linked. "M", "Cp", "n", and "X" are as previously defined.

Certain other modifications of this generalized reaction are apparent and come within the contemplated scope of the invention. For example, one may use enantiomerically enriched chiral metal starting materials (MY_(n)) to prepare enantiomerically enriched chiral ansa-metallocene derivatives directly. One may use excess X(CpH)₂ ligand to increase the yield and the rate of formation of the ansa-metallocene product (XCp₂ MY_(n-2)). In this regard one may use from 1 to 100 equivalents of HCpXCpH per equivalent of MY_(n). Further as demonstrated in some of the examples below one may have a "one pot" synthesis of XCp₂ MY_(n-2) from X(CpH)₂ and M(NRR')_(n) without isolation of XCp₂ M(NRR')_(n-2). This may provide a more economical catalyst synthesis. Each of these as well as other variations that readily come to the mind of one of ordinary skill in the art after knowing the basic reaction fall within the contemplated scope of the invention.

The following examples are offered to further illustrate but not limit the process of the present invention.

EXAMPLE

The ansa-metallocene rac-(EBI)Zr(NMe₂)₂ has been prepared in high yield from Zr(NMe₂)₄ and (EBI)H₂ (eq. 3). In a typical reaction, under N₂ atmosphere, Zr(NMe₂)₄ (0.50 g, 1.9 mmol) and (EBI)H₂ (0.48 g, 1.9 mmol) were placed in a Schlenk vessel containing a Teflon stir bar. Toluene (50 ml) was added. The reaction mixture was stirred and heated to 100° C. for 17 hours. During this period, the HNMe₂ co-product was allowed to escape freely (via an oil bubbler) from the reaction vessel. Removal of solvent under reduced pressure afforded an orange solid which was shown by 1H NMR to be (EBI)Zr(NMe₂)₂ in a rac/meso ratio of 10/1, in 90% yield. Recrystallization from hexane afforded pure rac-(EBI)Zr(NMe₂)₂ in 73% isolated yield (0.59 g). The rac-(EBI)Zr(NMe₂)₂ was characterized by ¹ H and ¹³ C NMR, elemental analysis, and an X-ray crystal structure determination.

It was also shown that rac-(EBI)Zr(NMe₂)₂ reacts with two equivalents of Me₂ NH·HCl to give rac-(EBI)ZrCl₂ in high isolated yield (eq. 5). In a typical reaction, under N₂ atmosphere, a solution of Me₂ NH·HCl (0.093 g, 1.14 mmol) in CH₂ Cl₂ (20 ml) was added dropwise to a stirred solution of rac-(EBI)ZR(nmE₂)₂ (0.25 g, 0.57 mmol) at -78° C. The resulting clear, yellow solution was stirred at room temperature for 30 mins. The solvent was removed under reduced pressure and the resulting solid was washed with hexane (15 ml) and extracted with toluene (70 ml). Removal of the solvent from the toluene extract under reduced pressure gave pure rac-(EBI)ZrCl₂ in 92% isolated yield (0.22 g). ##STR6##

The following additional examples 2-11 were run using the basic synthesis shown in Example 1 and are presented here for succinctness in table form.

                                      TABLE     __________________________________________________________________________     Synthesis of rac-(EBI)Zr(NMe.sub.2).sub.2 in high yield.                                (EBI)Zr(NMe.sub.2).sub.2                                         rac/meso                                              % isolated                     reaction   as %     ratio of                                              rac-     Example      temp                     time system                                of crude crude                                              (EBI)Zr(NMe.sub.2).sub.2     No.  solvent (°C.)                     (hours)                          used  product  product                                              (crystallized form)     __________________________________________________________________________     2    toluene 100                     48   N.sub.2                                90       1/1  25 (toluene)                          purge.sup.(a)     3    toluene 100                     26   partial N.sub.2                                80       4/1  --                          purge.sup.(b)     4    toluene 100                     17   N.sub.2                                90       1/1  --                          purge.sup.(a)     5    chlorobenzene                  125                     17   open.sup.(c)                                90       9/1  70 (hexane)     6    toluene 100                     117  open.sup.(c)                                <60      60/1 --     7    toluene 100                     12   pressure                                85       10/1 75 (toluene)                          release.sup.(d)     8    toluene 100                     18   closed.sup.(e)                                50       1/1  --     9    toluene 100                     17   open.sup.(c)                                90       13/1 68 (toluene)     10   toluene 100                     18   open, 90       13/1 --                          dark.sup.(f)     11   THF     67 20   open.sup.(c)                                50       2/1  --     __________________________________________________________________________      .sup.(a) N.sub.2 bubbled through reaction solution to drive off HNMe.sub.      as it is formed      .sup.(b) N.sub.2 bubbled through reaction solution only for part of      reaction time      .sup.(c) HNMe.sub.2 allowed to escape freely (via an oil bubbler) from      reaction vessel      .sup.(d) HNMe.sub.2 allowed to escape from reaction vessel via a mercury      bubbler      .sup.(e) closed system, HNMe.sub.2 is retained in reaction vessel      .sup.(f) as for (c) except reaction vessel wrapped in aluminum foil to      exclude light

EXAMPLE 12 "One-pot" synthesis of rac-(EBI)ZrCl₂ from Zr(NMe₂)₄

Zr(NMe₂)₄ (0.52 g, 1.9 mmol) and (EBI)H₂ (0.50 g, 1.9 mmol) were placed in a Schlenk vessel and chlorobenzene (10 ml) was added. The reaction mixture was stirred and heated to 125° C. for 18 h, and Me₂ NH was allowed to escape freely (via an oil bubbler) from the reaction vessel. An aliquot was removed and analyzed by ¹ H NMR. The ¹ H NMR spectrum showed that (EBI)Zr(NMe₂)₂ was present in 95% yield in a rac/meso ratio of 10/1. The reaction mixture was cooled to 0° C. and a solution of Me₂ NH·HCl (0.30 g, 3.7 mmol) in CH₂ Cl₂ (65 ml) was added dropwise over 30 min., during which time the color changed from red/orange to yellow. The reaction mixture was stirred at room temperature for 3 h. The solvent was removed under reduced pressure to give a yellow powder. Recrystallization of the yellow powder from CH₂ Cl₂ gave pure rac-(EBI)ZrCl₂ in 69% yield (0.54 g).

EXAMPLE 13 Simplified synthesis, and characterization data, for rac-(EBI)Zr(NMe₂)₂

Zr(NMe₂)₄ (1.0 g, 3.7 mmol) and (EBI)H₂ (0.96 g, 3.7 mmol) were placed in a Schlenk vessel, and toluene (20 ml) was added. The reaction mixture was stirred and heated to 100° C. for 17 h, and Me₂ NH was allowed to escape freely (via an oil bubbler) from the reaction vessel. An aliquot was removed and analyzed by ¹ H NMR. The ¹ H NMR spectrum showed that (EBI)Zr(NMe₂)₂ was present in 90% yield in a rac/meso ratio of 13/1. The reaction mixture was filtered, concentrated under reduced pressure and cooled to -20° C. Filtration afforded pure rac-(EBI)Zr(NMe₂)₂ as orange/red crystals in 68% yield (1.1 g).

rac-(EBI)Zr(NMe₂)₂ : Calcd. for C₂₄ H₂₈ N₂ Zr: C, 66.16; H, 6.48; N, 6.43. Found: C, 66.42; H, 6.40; N, 6.24. ¹ H NMR (360 MHz, C₆ D₆, 298K): 6 7.42 (d,J=9 Hz, 2 H, indenyl), 7.40 (d,J=9 Hz, 2 H, indenyl), 6.93 (dd,J=7 Hz,J=9 Hz, 2 H, indenyl), 6.71 (dd,J=7 Hz,J=9 Hz, 2 H, indenyl), 6.35 (d,J=3 Hz, 2 H, C₅ indenyl), 5.88 (d,J=3 Hz, 2 H, C₅ indenyl), 3.31 (m, 2 H, CH₂), 3.10 (m, 2 H, CH₂), 2.53 (s, 12 H, NMe₂). ¹³ C{¹ H} NMR (90 MHz, C₆ D₆, 298K): δ130.0 (C), 125.8 (CH), 123.3 (CH), 123.2 (CH), 121.3 (C), 120.7 (CH), 117.3 (C), 113.9 (CH), 100.6 (CH), 47.7 (NMe₂), 28.9 (CH₂ CH₂).

EXAMPLE 14 Use of nonane as a solvent for the synthesis of rac-(EBI)Zr(NMe₂)₂

Zr(NMe₂)₄ (1.0 g, 3.9 mmol) and (EBI)H₂ (1.0 g, 3.9 mmol) were placed in a Schlenk vessel containing a Teflon stir bar. Nonane (70 ml) was added. The reaction mixture was stirred and heated to 150° C. for 13 hours. An aliquot was removed and analyzed by ¹ H NMR. The ¹ H NMR spectrum showed that (EBI)Zr(NMe₂)₂ was present in a rac/meso ratio of 11/1, in 90% yield. Concentration of the reaction solution under reduced pressure, filtration, and cooling to -20° C. afforded pure rac-(EBI)Zr(NMe₂)₂ as an orange/red solid which was isolated by filtration in 55% yield (0.93 g).

EXAMPLE 15 Use of mixed amide compounds; Reaction of (EBI)H₂ and Zr(NMe₂)₂ (NPr^(i) ₂)₂

Zr(NMe₂)₂ (NPr^(i) ₂)₂ (0.50 g, 1.3 mmol)¹ and (EBI)H₂ (0.34 g, 1.3 mmol) were placed in a Schlenk vessel, and toluene (30 ml) was added. The reaction mixture was stirred and heated to 100° C. for 18 h, with the Schlenk vessel open to an oil bubbler. An aliquot was removed and analyzed by ¹ H NMR. The ¹ H NMR spectrum showed the presence of starting materials and a mixture of products. The toluene was removed under reduced pressure and m-xylene (10 ml) was added. The reaction mixture was then stirred and heated to 140° C. for 16 hours, after which time the ¹ H NMR spectrum of an aliquot showed that (EBI)Zr(NMe₂)₂ was present in 70% yield, in a rac/meso ratio of 2/1.

(1) Bradley, D. C.; Thomas, I. M. Proc. Chem. Soc. 1959, 225; J. Chem. Soc. 1960, 3857.

EXAMPLE 16 Synthesis and characterization of rac-(EBI)Hf(NMe₂)₂

Hf(NMe₂)₄ (1.1 g, 3.0 mmol) and (EBI)H₂ (0.78 g, 3.0 mmol) were placed in a Schlenk vessel, and toluene (25 ml) was added. The reaction mixture was stirred and heated to 105° C. for 18 h, and Me₂ NH was allowed to escape freely (via an oil bubbler) from the reaction vessel. An aliquot was removed and analyzed by ¹ H NMR. The ¹ H NMR spectrum showed only 10% conversion (based on Hf) to rac-(EBI)Hf(NMe₂)₂, 40% conversion to the binuclear species (μη⁵ :η⁵ --EBI){Hf(NMe₂)₃ }₂ and 50% conversion to the mononuclear intermediate (Me₂ N)₃ Hf(η⁵ --C₉ H₆ CH₂ CH₂ C₉ H₇). The toluene was removed under reduced pressure and m-xylene (20 ml) was added. The reaction mixture was then stirred and heated to 140° C. for 60 hours, after which time the ¹ H NMR spectrum of an aliquot showed that (EBI)Hf(NMe₂)₂ was present in 80% yield, in a rac/meso ratio of 16/1. Recrystallization from hexane afforded rac-(EBI)Hf(NMe₂)₂ as a yellow crystalline solid in 29% yield (0.46 g).

rac-(EBI)Hf(NMe₂)₂ : Calcd. for C₂₄ H₂₈ N₂ Hf: C, 55.12; H, 5.40; N, 5.36. Found: C, 54.99; H, 5.51; N, 5.28. ¹ H NMR (360 MHz, C₆ D₆, 298 K): δ7.43 (d,J=8 Hz, 2 H, indenyl), 7.40 (d,J=8 Hz, 2 H, indenyl), 6.93 (m, 2 H, indenyl), 6.74 m, 2 H, indenyl), 6.26 (d,J=3 Hz, 2 H, C₅ indenyl), 5.80 (d,J=3 Hz, 2 H, C₅ indenyl), 3.27 (m, 4 H, CH₂ CH₂), 2.56 (s, 12 H, NMe₂). ¹³ C{¹ H} NMR (90 MHz, C₆ D₆, 298K): δ130.2 (C), 125.5 (CH), 123.5 (CH), 123.3 (CH), 121.0 (C), 120.6 (CH), 115.8 (C), 113.1 (CH), 98.6 (CH), 47.2 (NMe₂), 28.4 (CH₂ CH₂).

EXAMPLE 17 Improved Synthesis of rac-(EBI)Hf(NMe₂)₂

Hf(NMe₂)₄ (0.53 g, 1.5 mmol) and (EBI)H₂ (0.39 g, 1.5 mmol) were placed in a Schlenk vessel, and m-xylene (15 ml) was added. The reaction mixture was stirred and heated to 140° C. for 21 h, and Me₂ NH was allowed to escape freely (via an oil bubbler) from the reaction vessel. An aliquot was removed and analyzed by ¹ H NMR. The ¹ H NMR spectrum showed 85% conversion (based on Hf) to (EBI)Hf(NMe₂)₂ with a rac/meso ratio of 7/1. Recrystallization from Et₂ O afforded pure rac-(EBI)Hf(NMe₂)₂ as a yellow crystalline solid in 53% yield (0.42 g).

EXAMPLE 18 Reaction of Hf(NMe₂)₄ with excess (EBI)H₂

Hf(NMe₂)₄ (0.35 g, 1.0 mmol) and (EBI)H₂ (2.6 g, 10 mmol) were placed in a Schlenk vessel, and toluene (10 ml) was added. The reaction mixture was stirred and heated to 105° C. for 18 h, and Me₂ NH was allowed to escape freely (via an oil bubbler) from the reaction vessel. An aliquot was removed and analyzed by ¹ H NMR. The ¹ H NMR spectrum showed 60% conversion (based on Hf) to (EBI)Hf(NMe₂)₂ (rac/meso ratio=8/1), 40% conversion to (Me₂ N)₃ Hf(η⁵ --C₉ H₆ CH₂ CH₂ C₉ H₇) and none of the binuclear species (μ--η⁵ :η⁵ --EBI) {Hf(NMe₂)₃ }₂. This compares with 10% conversion to (EBI)Hf(NMe₂)₂, 50% conversion to (Me₂ N)₃ Hf(η⁵ -C₉ H₆ CH₂ CH₂ C₉ H₇) and 40% conversion to (μ--η⁵ :η⁵ --EBI) {Hf(NMe₂)₃ }₂ when 1 equivalent of (EBI)H₂ was used. Thus, in the presence of 10 equivalents of (EBI)H₂ there is a 6-fold increase in the rate of formation of (EBI)Hf(NMe₂)₂.

EXAMPLE 19 Synthesis and characterization of rac-Me₂ Si(1-C₅ H₂ -2-Me-4-tBu)Zr(NMe₂)₂

Zr(NMe₂)₄ (0.93 g, 3.5 mmol) and dimethylbis(2-methyl-4-t-butylcyclopentadienyl)silane (1.0 g, 3.0 mmol), were placed in a Schlenk vessel, and toluene (25 ml) was added. The reaction mixture was stirred and heated to 100° C. for 5 h, and Me₂ NH was allowed to escape freely (via an oil bubbler) from the reaction vessel. An aliquot was removed and analyzed by ¹ H NMR. The ¹ H NMR spectrum showed that Me₂ Si(1-C₅ H₂ -2-Me-4-tBu)Zr(NMe₂)₂ was present in 90% yield in a rac/meso ratio of 2.5/1.

Recrystallization from hexane afforded pure rac-Me₂ Si(1-C₅ H₂ -2-Me-4-tBu)Zr(NMe₂)₂ in 52% yield (0.80 g) as a yellow crystalline solid.

rac-Me₂ Si(1-C₅ H₂ -2-Me-4-tBu)Zr(NMe₂)₂ : Anal. Calcd. for C₂₆ H₄₆ N₂ SiZr: C, 61.72; H, 9.16; N, 5.54. Found: C, 61.67; H, 9.25; N, 5.40. ¹ H NMR (360 MHz, C₆ D₆, 298K): δ6.27 (d,J=2 Hz, 2 H, C₅ H₂) 5.57 (d,J=2 Hz, 2 H, C₅ H₂), 2.70 (s, 12 H, NMe₂), 2.06 (s, 6 H, Me), 1.34 (s, 18 H, t-Bu), 0.57 (s, 6 H, SiMe₂). ¹³ C{¹ H} NMR (90 MHz, C₆ D₆, 298K): δ147.7 (C), 126.0 (C), 115.0 (CH), 106.1 (CH), 106.0 (C), 49.3 (NMe₂), 33.3 (C(CH₃)3), 32.0 (C(CH₃)₃), 17.0 (CH₃), -0.8 (SiMe₂).

EXAMPLE 20 Synthesis and characterization of rac-Me₂ Si(1-C₅ H₂ -2-Me-4-tBu)Zr(NC₄ H₈)₂

A solution of dimethylbis(2-methyl-4-t-butylcyclopentadienyl)silane (0.33 g, 1.0 mmol) in m-xylene (12 ml) was added to a solution of Zr(NC₄ H₈)₄ (0.38 g, 1.0 mmol) in m-xylene (12 ml). The reaction solution was stirred and heated to 90° C. for 4 hours, with a flow of N₂ bubbling through the reaction solution to drive off the pyrrolidine co-product. An aliquot was removed and analyzed by ¹ H NMR. The ¹ H NMR spectrum showed that Me₂ Si(1-C₅ H₂ -2-Me-4-tBu)Zr(NC₄ H₈)₂ was present in 70% yield in a rac/meso ratio of 3/1. Recrystallization from hexane afforded pure rac-Me2Si(1-C₅ H₂ -2-Me-4-tBu)Zr(NC₄ H₈)₂ in 39% yield (0.22 g) as a yellow crystalline solid. The structure of this compound was confirmed by X-ray crystallography.

rac-Me₂ Si(1-C₅ H₂ -2-Me-4-tBu)Zr(NC₄ H₈)₂ : Anal. Calcd. for C₃₀ H₅₀ N₂ SiZr: C, 64.57; H, 9.03; N, 5.02. Found: C, 64.66; H, 9.23; N, 4.91. ¹ H NMR (360 MHz, C₆ D₆, 298K): δ6.18 (d,J=2 Hz, 2 H, C₅ H₂), 5.71 (d,J=2 Hz, 2 H, C₅ H₂), 3.30 (m, 4 H, NCH₂), 3.21 (m, 4 H, NCH₂), 2.12 (s, 6 H, Me.), 1.60 (m, 4 H, CH₂), 1.49 (m, 4 H, CH₂), 1.33 (s, 18 H, t-Bu), 0.57 (s, 6 H, SiMe₂). ¹³ C{¹ H} NMR (gdV073.2) (90 MHz, C₆ D₆, 298 K): δ147.8 (C), 126.1 (C), 116.0 (CH), 105.9 (C), 105.8 (CH), 56.8 (NCH₂), 33.1 (C(CH₃)₃), 32.0 (C(CH₃)₃), 26.1 (CH₂), 16.7 (CH₃), -0.7 (SiMe₂).

EXAMPLE 21 Synthesis of rac-(SBI)Zr(NMe₂)₂ (SBI═Me₂ Si(1-idenyl)₂)

A Schlenk vessel was charged with dimethylbis(1-indenyl)silane ((SBI)H₂), (1.00 g, 3.47 mmol) and Zr(NMe₂)₄ (0,927 g, 3.47 mmol), m-xylene (20 ml) was added, and the mixture was stirred for 11 h at 140° C. Me₂ NH was allowed to escape freely (via an oil bubbler) from the reaction vessel. An aliquot was removed and analyzed by ¹ H NMR. The ¹ H NMR spectrum showed that (SBI)Zr(NMe₂)₂ was present in 85% crude yield in a rac/meso ratio of 7/1. The solvent was removed under reduced pressure affording a red-orange oily solid. The solid was extracted with hexane (110 ml), and the extract was filtered, concentrated to 30 ml, and cooled to -80° C. After 5 days red-orange crystals of pure rac-(SBI)Zr(NMe₂)₂ were collected by filtration and dried under vacuum (502 mg, 31.0%). The structure of rac-(SBI)Zr(NMe₂)₂ was confirmed by X-ray crystallography. Anal. Calcd. for C₂₄ H₃₀ N₂ SiZr: C, 61.88; H, 6.49; N, 6.01. Found: C, 61.60; H, 6.31; N, 5.87. ¹ H NMR (360 MHz, C₆ D₆ 298K): δ7.58 (d,J=8 Hz, 2 H, indenyl), 7.51 (d,J=8 Hz, 2 H, indenyl), 6.95 (pseudo t,J=7 Hz, 2 H, indenyl), 6.86 (d,J=3 Hz, 2 H, C₅ indenyl), 6.70 (pseudo t,J=7 Hz, 2 H, indenyl), 6.21 (d,J=3 Hz, 2 H, C₅ indenyl), 2.48 (s, 12 H, NMe₂), 0.79 (s, 6 H, SiMe₂). ¹³ C{¹ H} NMR (90 MHz, toluene-d₈, 298K): δ135.1 (C), 131.2 (C), 125.8 (CH), 124.1 (CH), 124.0 (CH), 122.9 (CH), 115.8 (CH), 109.9 (CH), 97.9 (C), 47.8 (NMe₂), -1.4 (SiMe₂).

EXAMPLE 22 Synthesis of rac-(SBI)ZrMe₂

A solution of rac-(SBI)Zr(NMe₂)₂ (0.416 g, 0.893 mmol) in toluene (15 ml) was added dropwise to a solution of AlMe₃ (0.519 g, 7.20 mmol) in toluene (15 ml) over 15 minutes to give a yellow-orange solution. The solution was stirred for 3 hours at room temperature. The toluene was removed under reduced pressure yielding a pale yellow solid. ¹ H NMR analysis showed greater than 90% conversion to rac-(SBI)ZrMe₂. The solid was washed with hexanes (2×20 ml) at 0° C. and then dried for 20 hours under vacuum. Recrystallization from THF at -60° C. for 24 hours afforded rac-(SBI)ZrMe₂ as a pale yellow solid which was collected by filtration and dried under vacuum (53 mg, 15%). ¹ H NMR (360 MHz, CD₂ Cl₂) δ7.62 (d,J=9 Hz, 2 H, indenyl), 7.38 (d,J=9 Hz, 2 H, indenyl), 7.25 (pseudo t,J=8 Hz, 2 H, indenyl), 6.98 (pseudo t,J=8 Hz, 2 H, indenyl), 6.84 (d, J=3 Hz, 2 H, C₅ indenyl), 5.92 (d,J=3 Hz, 2 H, C₅ indenyl), 0.91 (s, 6 H, SiMe₂), -1.43 (s, 6 H, ZrMe₂). This compound was prepared previously by a different route (see Bochmann, M.; Lancaster, S.; Hursthouse, B.; Malik, K. M. Organometallics 1994, 13, 2235-2243).

It can therefore be seen that the invention accomplishes all of its stated objectives in that ansa-metallocenes were prepared in pure rac form in high yields without the use of ansa-bis-cyclopentadienyl dianion reagents. The yields are substantially higher than the traditional prior art yields of 10% to 30%. 

What is claimed is:
 1. A process of synthesizing in high yield ansa-metallocene complexes of the formula: ##STR7## wherein Cp independently and in each occurrence is cyclopentadienyl, indenyl, fluorenyl, or a related group that can π-bond to the metal, or a hydrocarbyl, alkyl, aryl, silyl, halo, halohydrocarbyl, hydrocarbylmetalloid, or halohydrocarbylmetalloid substituted derivative of said cyclopentadienyl, indenyl, fluorenyl or related group, X is a bridging group which links the Cp groups, M is a metal selected from the group consisting of Group 3, 4 and 5 metals, Y is a leaving group wherein each Y moiety may be the same or different or linked, and n is from 3 to 5, said process comprising:reacting an ansa-bis-cyclopentadiene, indene, fluorene or related group as defined above with a metal leaving group complex MY_(n) to provide a high yield of ansa-metallocene complex.
 2. The process of claim 1 wherein the metal leaving group complex, MY_(n), is a metal amide M(NRR')_(n) of a Group 4 metal and R and R' are each hydrogen, hydrocarbyl radicals of from C₁ to C₂₀ or silyl radicals and R and R' may be the same or different or linked.
 3. The process of claim 1 wherein M is a Group 4 metal selected from the group consisting of zirconium, titanium and hafnium.
 4. The process of claim 3 wherein the metal is zirconium.
 5. The process of claim 3 wherein the metal is hafnium.
 6. The process of claim 1 wherein Y is selected from the group consisting of NRR', R, OR, SR, PRR', F, Cl, Br, I, OC(O)R, OS(O)₂ R and may be the same or different or linked and R and R' are each hydrogen, or hydrocarbyl radicals of from C₁ to C₂₀ or silyl radicals, and R and R' may be the same, different or linked.
 7. The process of claim 6 wherein Y is a NRR' group.
 8. The process of claim 7 wherein R and R' are independently C₁ to C₄ alkyl, and may be the same, different or linked.
 9. The process of claim 8 wherein R and R' are methyl.
 10. The process of claim 9 wherein the gaseous byproduct dimethylamine is not swept away from the reaction as it is produced.
 11. The process of claim 1 wherein said process is conducted at a temperature ranging from -80° C. to 250° C.
 12. The process of claim 11 wherein said process is conducted at a temperature ranging from 25° C. to 250° C.
 13. The process of claim 12 wherein the temperature is from 80° C. to 160° C.
 14. The process of claim 1 wherein the reaction is conducted in the presence of a nonaqueous, non-alcoholic organic solvent.
 15. The process of claim 14 wherein the solvent is selected from the group consisting of hydrocarbons, toluene, ethers, chlorinated hydrocarbons and tetrahydrofuran.
 16. The process of claim 1 where X is ethylene and Cp is indenyl.
 17. The process of claim 1 wherein X is methylene or substituted methylene.
 18. The process of claim 1 wherein X is silylene or substituted silylene.
 19. The process of claim 1 wherein an excess of the ansa-bis-cyclopentadiene, indene, fluorene, or substituted derivative, is used.
 20. The process of claim 1 wherein X is SiMe₂.
 21. A process of synthesizing in high yield ansa-metallocene complexes of the formula: ##STR8## wherein Cp independently and in each occurrence is cyclopentadienyl, indenyl, fluorenyl, or a related group that can π-bond to the metal, or a hydrocarbyl, alkyl, aryl, silyl, halo, halohydrocarbyl, hydrocarbylmetalloid, or halohydrocarbylmetalloid substituted derivative of said cyclopentadienyl, indenyl, fluorenyl or related group, X is a bridging group which links the Cp groups, M is a metal selected from the group consisting of Group 3, 4 and 5 metals, Y is a leaving group wherein each Y moiety may be the same or different or linked and n is from 3 to 5, said process comprising:reacting an ansa-bis-cyclopentadiene, indene, fluorene or related group as defined above with a metal leaving group complex MY_(n) to provide a high yield of ansa-metallocene complex and isolating the ansa-metallocene complex from the reaction mixture.
 22. The process of claim 21 wherein the metal leaving group complex, MY_(n), is a metal amide M(NRR')_(n) of a Group 4 metal and R and R' are each hydrogen, hydrocarbyl radicals of from C₁ to C₂₀ or silyl radicals and R and R' may be the same or different or linked.
 23. The process of claim 22 wherein the metal is zirconium and n is
 4. 24. The process of claim 22 wherein the metal is hafnium and n is
 4. 25. The process of claim 22 wherein R and R' are both methyl.
 26. The process of claim 22 wherein X is an ethylene moiety and Cp is indenyl.
 27. The process of claim 22 wherein X is silylene or substituted silylene.
 28. The process of claim 27 wherein X is SiMe₂.
 29. The process of claim 22 wherein R and R' are methyl and the gaseous byproduct dimethylamine is not swept away from the reaction as it is produced.
 30. A process of synthesizing in high yield rac ansa-metallocene complexes of the formula: ##STR9## wherein Cp independently and in each occurrence is a substituted cyclopentadienyl, indenyl, fluorenyl, or a related group that can π-bond to the metal, or a hydrocarbyl, alkyl, aryl, silyl, halo, halohydrocarbyl, hydrocarbylmetalloid, or halohydrocarbylmetalloid substituted derivative of said cyclopentadienyl, indenyl, fluorenyl or related group, X is a bridging group which links the Cp groups, M is a metal elected from the group consisting of Group 3, 4 and 5 metals, Y is a leaving group wherein each Y moiety may be the same or different or linked, and n is from 3 to 5, said process comprising:reacting an ansa-bis-cyclopentadiene, indene, fluorene or related group as defined above with a metal leaving group complex MY_(n) to provide a high yield of rac ansa-metallocene complex.
 31. The process of claim 30 wherein the metal leaving group complex (MY_(n)) is a metal amide complex of a Group 4 metal and R and R' are each hydrogen, hydrocarbyl radicals of from C₁ to C₂₀ or silyl radicals, and R and R' may be the same, different or linked.
 32. The process of claim 31 which includes as an additional step isolating the rac ansa-metallocene complex.
 33. The process of claim 31 wherein X is ethylene and Cp is indenyl.
 34. The process of claim 7 which includes a step of converting the ansa-metallocene amide complex to an ansa-metallocene chloride complex, XCp₂ MCl_(n-2), an ansa metallocene alkyl complex, XCp₂ M(R)_(n-2), or other XCp₂ MY_(n-2) derivatives.
 35. The process of claim 31 wherein X is silylene or substituted silylene.
 36. The process of claim 1 wherein an enantiomerically enriched chiral metal leaving group complex (MY_(n)) is used to prepare an enantiomerically enriched chiral ansa-metallocene product.
 37. A process of synthesizing in high yield ansa-metallocene complexes of the formula: ##STR10## wherein Cp independently and in each occurrence is cyclopentadienyl, indenyl, fluorenyl, or a related group that can π-bond to the metal, or a hydrocarbyl, alkyl, aryl, silyl, halo, halohydrocarbyl, hydrocarbylmetalloid, or halohydrocarbylmetalloid substituted derivative of said cyclopentadienyl, indenyl, fluorenyl or related group, X is methylene or substituted methylene which links the Cp groups, M is a metal selected from the group consisting of Group 3, 4 and 5 metals, Y is a leaving group wherein each Y moiety may be the same or different or linked, and n is from 3 to 5, wherein the metal leaving group complex, MY_(n), is a metal amide M(NRR')_(n) of a Group 4 metal and R and R' are each hydrogen, hydrocarbyl radicals of from C₁ to C₂₀ or silyl radicals and R and R' may be the same or different or linked, said process comprising:reacting an ansa-bis-cyclopentadiene, indene, fluorene or substituted derivative as defined above with a metal leaving group complex MY_(n) to provide a high yield of ansa-metallocene complex and isolating the ansa-metallocene complex from the reaction mixture. 